/**
 * The Units of Measure API, UCUM codes, UCUM table (regardless of format),
 * and UCUM Specification are copyright © 1999-2010,
 * Regenstrief Institute, Inc. and the Unified Codes for Units of Measures
 * (UCUM) Organization. All rights reserved.
 *
 * See TermsOfUse for details.
 */
package org.unitsofmeasure;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.HashMap;
import java.util.concurrent.ConcurrentHashMap;
import java.util.logging.Level;
import java.util.logging.Logger;

import org.unitsofmeasure.Quantity;
import org.unitsofmeasure.Unit;
import org.unitsofmeasure.quantity.*;

/**
 * A factory producing simple quantities instances (tuples {@link Number}/
 * {@link AbstractUnit}).
 * 
 * For example:[code] Mass m =
 * QuantityFactory.getInstance(Mass.class).create(23.0, KILOGRAM); // 23.0 kg
 * Time m = QuantityFactory.getInstance(Time.class).create(124, MILLI(SECOND));
 * // 124 ms [/code]
 * 
 * @param <Q>
 *            The type of the quantity.
 * 
 * @author <a href="mailto:desruisseaux@users.sourceforge.net">Martin
 *         Desruisseaux</a>
 * @author <a href="mailto:jcp@catmedia.us">Werner Keil</a>
 * @author <a href="mailto:jean-marie@dautelle.com">Jean-Marie Dautelle</a>
 * @version 1.0.8 ($Revision: 47 $), $Date: 2010-07-04 12:32:52 +0100 (So, 04
 *          Jul 2010) $
 */
abstract class QuantityFactory<Q extends Quantity<Q>> {

    /**
     * Holds the current instances.
     */
    @SuppressWarnings("unchecked")
    private static final ConcurrentHashMap<Class, QuantityFactory> INSTANCES = new ConcurrentHashMap<Class, QuantityFactory>();

    private static final Logger logger = Logger.getLogger(QuantityFactory.class
	    .getName());

    private static final Level LOG_LEVEL = Level.FINE;

    /**
     * Returns the default instance for the specified quantity type.
     * 
     * @param <Q>
     *            The type of the quantity
     * @param type
     *            the quantity type
     * @return the quantity factory for the specified type
     */
    @SuppressWarnings("unchecked")
    public static <Q extends Quantity<Q>> QuantityFactory<Q> getInstance(
	    final Class<Q> type) {

	logger.log(LOG_LEVEL, "Type: " + type + ": " + type.isInterface());
	QuantityFactory<Q> factory;
	if (!type.isInterface()) {
	    if (type != null && type.getInterfaces() != null
		    & type.getInterfaces().length > 0) {
		logger.log(LOG_LEVEL, "Type0: " + type.getInterfaces()[0]);
		Class<?> type2 = type.getInterfaces()[0];

		factory = INSTANCES.get(type2);
		if (factory != null)
		    return factory;
		if (!Quantity.class.isAssignableFrom(type2))
		    // This exception is not documented because it should never
		    // happen if the
		    // user don't try to trick the Java generic types system
		    // with unsafe cast.
		    throw new ClassCastException();
		factory = new Default<Q>((Class<Q>) type2);
		INSTANCES.put(type2, factory);
	    } else {
		factory = INSTANCES.get(type);
		if (factory != null)
		    return factory;
		if (!Quantity.class.isAssignableFrom(type))
		    // This exception is not documented because it should never
		    // happen if the
		    // user don't try to trick the Java generic types system
		    // with unsafe cast.
		    throw new ClassCastException();
		factory = new Default<Q>(type);
		INSTANCES.put(type, factory);
	    }
	} else {
	    factory = INSTANCES.get(type);
	    if (factory != null)
		return factory;
	    if (!Quantity.class.isAssignableFrom(type))
		// This exception is not documented because it should never
		// happen if the
		// user don't try to trick the Java generic types system with
		// unsafe cast.
		throw new ClassCastException();
	    factory = new Default<Q>(type);
	    INSTANCES.put(type, factory);
	}
	return factory;
    }

    /**
     * Overrides the default implementation of the factory for the specified
     * quantity type.
     * 
     * @param <Q>
     *            The type of the quantity
     * @param type
     *            the quantity type
     * @param factory
     *            the quantity factory
     */
    @SuppressWarnings("unchecked")
    protected static <Q extends Quantity> void setInstance(final Class<Q> type,
	    QuantityFactory factory) {
	if (!Quantity.class.isAssignableFrom(type))
	    // This exception is not documented because it should never happen
	    // if the
	    // user don't try to trick the Java generic types system with unsafe
	    // cast.
	    throw new ClassCastException();
	INSTANCES.put(type, factory);
    }

    /**
     * Returns the quantity for the specified number stated in the specified
     * unit.
     * 
     * @param value
     *            the value stated in the specified unit
     * @param unit
     *            the unit
     * @return the corresponding quantity
     */
    public abstract Q create(Number value, Unit<Q> unit);

    /**
     * Returns the metric unit for quantities produced by this factory or
     * <code>null</code> if unknown.
     * 
     * @return the metric units for this factory quantities.
     */
    public abstract Unit<Q> getMetricUnit();

    /**
     * The default factory implementation. This factory uses reflection for
     * providing a default implementation for every {@link QuantityAmount}
     * sub-types.
     * 
     * @param <Q>
     *            The type of the quantity
     */
    private static final class Default<Q extends Quantity<Q>> extends
	    QuantityFactory<Q> {

	/**
	 * The type of the quantities created by this factory.
	 */
	private final Class<Q> type;

	/**
	 * The metric unit for quantities created by this factory.
	 */
	private final Unit<Q> metricUnit;

	/**
	 * Creates a new factory for quantities of the given type.
	 * 
	 * @param type
	 *            The type of the quantities created by this factory.
	 */
	@SuppressWarnings("unchecked")
	Default(final Class<Q> type) {
	    this.type = type;
	    metricUnit = CLASS_TO_METRIC_UNIT.get(type);
	}

	@SuppressWarnings("unchecked")
	static final HashMap<Class, Unit> CLASS_TO_METRIC_UNIT = new HashMap<Class, Unit>();
	static {
	    CLASS_TO_METRIC_UNIT.put(Dimensionless.class, AbstractUnit.ONE);
	    // CLASS_TO_METRIC_UNIT.put(Mass.class, KILOGRAM);
	    CLASS_TO_METRIC_UNIT.put(Length.class, DistanceUnit.REF_UNIT);
	    // CLASS_TO_METRIC_UNIT.put(AmountOfSubstance.class, MOLE);
	    // CLASS_TO_METRIC_UNIT.put(Time.class, SECOND);
	    // CLASS_TO_METRIC_UNIT.put(MagnetomotiveForce.class, AMPERE_TURN);
	    // CLASS_TO_METRIC_UNIT.put(Angle.class, RADIAN);
	    // CLASS_TO_METRIC_UNIT.put(SolidAngle.class, STERADIAN);
	    // CLASS_TO_METRIC_UNIT.put(Data.class, BIT);
	    // CLASS_TO_METRIC_UNIT.put(Frequency.class, HERTZ);
	    // CLASS_TO_METRIC_UNIT.put(Force.class, NEWTON);
	    // CLASS_TO_METRIC_UNIT.put(Pressure.class, PASCAL);
	    // CLASS_TO_METRIC_UNIT.put(Energy.class, JOULE);
	    // CLASS_TO_METRIC_UNIT.put(Power.class, WATT);
	    // CLASS_TO_METRIC_UNIT.put(ElectricCharge.class, COULOMB);
	    // CLASS_TO_METRIC_UNIT.put(ElectricPotential.class, VOLT);
	    // CLASS_TO_METRIC_UNIT.put(ElectricCapacitance.class, FARAD);
	    // CLASS_TO_METRIC_UNIT.put(ElectricResistance.class, OHM);
	    // CLASS_TO_METRIC_UNIT.put(ElectricConductance.class, SIEMENS);
	    // CLASS_TO_METRIC_UNIT.put(MagneticFlux.class, WEBER);
	    // CLASS_TO_METRIC_UNIT.put(MagneticFluxDensity.class, TESLA);
	    // CLASS_TO_METRIC_UNIT.put(ElectricInductance.class, HENRY);
	    // CLASS_TO_METRIC_UNIT.put(LuminousFlux.class, LUMEN);
	    // CLASS_TO_METRIC_UNIT.put(Illuminance.class, LUX);
	    // CLASS_TO_METRIC_UNIT.put(RadioactiveActivity.class, BECQUEREL);
	    // CLASS_TO_METRIC_UNIT.put(RadiationDoseAbsorbed.class, GRAY);
	    // CLASS_TO_METRIC_UNIT.put(RadiationDoseEffective.class, SIEVERT);
	    // CLASS_TO_METRIC_UNIT.put(CatalyticActivity.class, KATAL);
	    // CLASS_TO_METRIC_UNIT.put(Velocity.class, METRES_PER_SECOND);
	    // CLASS_TO_METRIC_UNIT.put(Acceleration.class,
	    // METRES_PER_SQUARE_SECOND);
	    // CLASS_TO_METRIC_UNIT.put(Area.class, SQUARE_METRE);
	    // CLASS_TO_METRIC_UNIT.put(Volume.class, CUBIC_METRE);
	}

	@Override
	@SuppressWarnings("unchecked")
	public Q create(final Number value, final Unit<Q> unit) {
	    // System.out.println("Type: " + type);
	    return (Q) Proxy
		    .newProxyInstance(type.getClassLoader(),
			    new Class<?>[] { type }, new GenericHandler<Q>(
				    value, unit));
	}

	@Override
	public Unit<Q> getMetricUnit() {
	    return metricUnit;
	}
    }

    /**
     * The method invocation handler for implementation backed by any kind of
     * {@link Number}. This is a fall back used when no specialized handler is
     * available for the number type.
     */
    private static final class GenericHandler<Q extends Quantity<Q>> implements
	    InvocationHandler {
	final Unit<Q> unit;
	final Number value;

	GenericHandler(final Number value, final Unit<Q> unit) {
	    this.unit = unit;
	    this.value = value;
	}

	@SuppressWarnings("unchecked")
	public Object invoke(final Object proxy, final Method method,
		final Object[] args) {
	    final String name = method.getName();
	    if (name.equals("doubleValue")) { // Most frequent.
		final Unit<Q> toUnit = (Unit<Q>) args[0];
		if ((toUnit == unit) || (toUnit.equals(unit)))
		    return value.doubleValue(); // Returns value directly.
		return unit.getConverterTo(toUnit).convert(value.doubleValue());
	    } else if (name.equals("longValue")) {
		final Unit<Q> toUnit = (Unit<Q>) args[0];
		if ((toUnit == unit) || (toUnit.equals(unit)))
		    return value.longValue(); // Returns value directly.
		double doubleValue = unit.getConverterTo(toUnit).convert(
			value.doubleValue());
		if ((doubleValue < Long.MIN_VALUE)
			|| (doubleValue > Long.MAX_VALUE))
		    throw new ArithmeticException("Overflow: " + doubleValue
			    + " cannot be represented as a long");
		return (long) doubleValue;
	    } else if (name.equals("getValue")) {
		return value;
	    } else if (name.equals("getUnit")) {
		return unit;
	    } else if (name.equals("toString")) {
		final StringBuilder buffer = new StringBuilder();
		return buffer.append(value).append(' ').append(unit).toString();
	    } else if (name.equals("hashCode")) {
		return value.hashCode() * 31 + unit.hashCode();
	    } else if (name.equals("equals")) {
		final Object obj = args[0];
		if (!(obj instanceof Quantity))
		    return false;
		final Quantity that = (Quantity) obj;
		// if (!unit.isCompatible((AbstractUnit<?>) that.getUnit()))
		// return false;
		// return value.doubleValue() == (that).doubleValue(unit);
		return equals(that);
	    } else if (name.equals("compareTo")) {
		final Quantity that = (Quantity) args[0];
		// return Double.compare(value.doubleValue(),
		// that.doubleValue(unit));
		return equals(that);
	    } else {
		throw new UnsupportedOperationException(name);
	    }
	}
    }
}
